In the field of high energy (ionizing) radiation detection that operates at near-ambient temperatures with high spectroscopic energy resolution, detectors have a variety of uses, one of which is the field of nuclear nonproliferation and interdiction applications where high sensitivity, high energy resolution, and field capability are very important.
Various semiconductor materials have been investigated for use in the past to try to achieve high-resolution room temperature detectors, including most notably cadmium zinc telluride (CdZnTe) and cadmium telluride (CdTe); however, currently, no attempts have produced samples having all the characteristics desirable of large, single crystal detector materials, whether related to a lack in performance (resolution, absorption, size, etc.), and/or cost (for example, some crystal samples may cost $25,000 to $125,000 per crystal), etc. Specific performance criteria related to effective radiation detector crystals are described in more detail in the Detailed Description section. Efforts to find and fabricate new semiconductor materials to mitigate these issues are currently underway in a number of laboratories. However, to date, no material has been found which can produce the desired characteristics at room temperature.
Aluminum antimonide (AlSb) nominally meets the characteristics desirable of a single crystal detector material, including low-cost and high performance radiation detection at room temperature. A number of past efforts (of very limited success) have been aimed at producing this material in a form appropriate for radiation detection. However, the past efforts have had only limited success due to the lack of existing processes to create large single crystals with all of the below described properties, simultaneously. Particularly, achieving high resistivity with high carrier mobilities has not been possible with conventional production techniques. Consequently, no prior work has been able to demonstrate spectroscopic radiation detection of this material. Various past efforts included growth and annealing steps to produce AlSb material, but failed to control or understand the processes appropriately to produce material with the desired properties for use in radiation detection. Therefore, it would be beneficial to have a process of fabrication and use of AlSb which addresses the shortfalls currently encountered in conventional fabrication techniques.